I just heard on CNBC, French officials have made it more than clear that blown tyres during the take-off run ignited the fire that brought down the Air France Concorde. As Concorde takes-off at higher speeds than regualr jets, the tyres get blazing hot, and can sometimes explode violently. On one such event, a blown tyre blew a hole into a wing. The plane, obviously didn't crash. The gases, and chunks of rubber appear to have entered the engine intake, and started the fatal fire.

In related news, two more bodies have been found inside the hotel that Concorde crashed into.

The news is saying that the blown tires punctured a fuel tank, and the leaking gas caused a huge fire.
I guess, this is a lesson for Air france for not listening to NTSB warnings.
Can someone find out, how many BA concordes had tire blowouts ??

My theory is still what it was before. I believe that one of the engines, 1 or 2, had an uncontained blade separation. When that happened, shrapnel from this would be like a small bomb explosion. The shrapnel that went down, blew the tires, the shrapnel that went up, punctured the fuel tanks, and the shrapnel the went sideways, damaged the other engine. Remember that, on Concorde, the engines are paired almost as one.

I agree with Hmmmm.... on this one. As I said in an earlier post, I think it is too coincidental that the #2 engine (thrust reverser) was worked on just before the Concorde departed, and that happened to be the engine that initially failed. But, a failure of the tires and possibly a resulting failure in the gear assembly could certainly lead to a severing of the wing and fuel tanks. Regardless of the cause, it was a horrible tragedy, and hopefully we can learn from the experience and make sure it never happens again.

Funny how the cycle gets repeated every time an aircraft goes down the media is right there with the theory of the moment, which of course changes every time a new piece of evidence is uncovered. In the media's haste to fill-in airtime with "news" (or rather, their own perspective of it, constrained by the limits of their understanding of the many technical issues involved, not to mention that the wreckage hasn't cooled yet), the media also often overlooks the context of the information.

For example, take the thrust reverser revelation. Yep, it was reported as inop by the inbound crew (who "managed" to land without problem). Even though the inop reverser was deferrable by their minimum equipment list (MEL), i.e. you can fly without its use as long as restrictions (if any) are complied with, the outbound captain elected (as is his perrogative) to have the item repaired. What the media missed here was the thrust reverser, essentially, is a bolt-on accessory to the engine, and its presence has nothing to do with engine operation withrespect to the generation of thrust. It's used as a braking aid on landings or the rare aborted takeoff, and it's not used in flight. Yet, despite this, the media automatically assumes that since this item (on the number 2 engine) was worked on before takeoff, and the crew reported the number 2 engine had failed, that that's some kind of proof positive that the items are related.

This accident is quite amazing that there is such great photo evidence of the accident sequence. The most recnt pictures that show the near head-on shot of the takeoff roll and rotation are stunning, and telling. Based upon the info known/released at present, my opinion is that the central failure was one or more main gear tires, which led to the sencondary failures of the #2 and then #1 engines, as well as tire/wheel fragments striking the bottom of the wing and compromising the fuel tank.

It's about a NASA Conver 990 that aborted a takeoff back in the mid-1980s due to a main tire failure. Subsequent tire failures on the same gear truck eventually allowed the wheels themselves to contact the runway and start breaking up. One piece impacted the underside of the wing at nearly 200 mph as I recall, and the report photos clearly show the same type of fuel/fire flow as does the most recent Concorde photo. Such an impact from the tire/wheel below would have been a direct one, since it was perpendicular to the wing surface. It's thus difficult to imagine any supposed piece of Concorde engine exiting the pod and causing that level of damage, but certainly not impossible.

Bottom line is that engine failure(s) appear to be a consequence of the tire failure and fire, and not the other way around. Time will tell.

My belief that an engine failure was the initiating event is not based upon the media reporting the fact that the engine received some kind of service just before take-off. I don't know how a thrust reverser would play into this disaster. My contention is based only on the probability that an exploding engine, in my opinion, can do more damage than an exploding tire. It seems more plausible that an exploding engine would be the culprit. I would also expect that a tire would blow at the later stages of take-off when it gets the hottest. Conversly, I expect an engine failure at the beginning of the take-off roll as it is brought to full power. Eyewitness reports seem to indicate that the debris and flames started early on in the take-off.

But I am steeling myself for the possibility that I could be wrong. As unbelievable as that may seem.

If a tyre bursts and then the wheel hub shatters then there will be some heavy duty bits of metal flying around that could quite conceivably puncture the wing.

Whilst not discounting an uncontained engine failure I would point out that RR have considerable experince in containg a failure in such an engine configuaration, e.g Vickers Valiant, Handley-Page Victor, Avro Vulcan, D.H. Comet & to a certain extent the VC-10. Additionally the UK airframe design team also had similar experince on the above a/c (I don't know enough about the French side to comment on the French input).

This is the memo that NTSB sent French authorities back in 1981 after 4 Concorde tire failures between Jul 1979 and February 1981. Particularly noteworthy is their account of the June 4, 1979 incident where major damage occurred, including a fuel leak. The FAA link to this incident is in the link I forgot add added later in the thread above.

>>>My contention is based only on the probability that an exploding engine, in my opinion, can do more damage than an exploding tire.

It depends. Most engine failures are contained ones. Some are not, but only eject parts in small numbers and/or size. The even more rare ones eject entire fan sections (United 232 and that National DC-10 over ABQ; the Delta MD-88 at PNS) that really do some damage. I have yet to see any media mention of Concorde *engine* parts found on the runway, and since tire fragments were, that leads me to believe the tire was the the source of the initial failure. (Hey, I could be wrong too...)

>>>It seems more plausible that an exploding engine would be the culprit. I would also expect that a tire would blow at the later stages of take-off when it gets the hottest..

When tires fail due to heat, it's most often immediately after a vigorous application upon landing (or the more rare aborted takeoff) where the brakes have just been exposed to a few million-pounds of energy. True, the inbound flight had experienced inop thrust reversers arriving at Paris, and that crew presumably could have used the brakes more than a routine reverser-assisted landing, thus more energy and heat than usual, but certainly not more than an aborted takeoff. That built-up energy/heat translates to the tires, and depending upon several variables, the fuse plugs in the wheels could melt (and deflate the tires) anywhere from immediately or gradually over :45 or so, maybe longer. I'm supposing the Concorde's ground time was a couple of hours, thus any such problem would have been noticed before they pushed the gate.

>>>Conversly, I expect an engine failure at the beginning of the take-off roll as it is brought to full power.

Again, some do, some don't.

>>>Eyewitness reports seem to indicate that the debris and flames started early on in the take-off.

I think the key question are *how* early, and the *specific* debris. Brake release? Prior to V-1 and V-rotate? Afterwards? Was the debris tire-related or engine-related?

If the engine failed at the start of the takeoff role (your full-power scenario) that point would have been far below V-1, and the takeoff could have been aborted. If a tire (or tires) started to fail on the takeoff roll (which can be somewhat more insidous than an engine failure with its associated warning systems), irrespective of having reached V-1 or not, the tires could have come part and damaged the wing, or maybe even the wheels themselves doing likewise. Maybe the IAD tire fragment was smaller than the Paris tire (or wheel) fragments. Maybe the IAD flight was just luckier that an ignition source didn't set it off.

These are the kinds of answers that take investigators time to figure out, much to the disappointment of the media, who proceed to fill otherwise dead-airtime with usually uninformed speculations. Given the incredble photos of this accident, and the past experiences of Concorde susceptibility to secondary damage from blown tires (and the failure sequence seen in the NASA Convair 990 report, I still think the tire was the initial failure with fire and engine failure(s) as some very unfortunate dual consequences.

Not saying this to start a whizzing match by any means, but just to convey my opinion of what I see, and in the context of my personal operational experience (20+ years) on other types of airline aircraft. The Concorde is unique in many respects, but it also shares great commonalites with conventional aircraft.

The dramatic picture of concorde rotating in flames will linger in our minds for many months to come. Yes I beleive a catastrophic multiple tyre failure caused the pucture in the wing and the consequential fuel leak and fire. The theory of the engines ingesting debris is very plausible, especially since it is #2 that sustained the most damage. Does anyone know where I can find the 1979 report of the NTSB on the issue please ?

I wasn't able to find anything on the NTSB site, probably since was an incident (versus accident) and it occured before the 1983 records the NTSB site starts with. Over on the FAA incident database, they have this, but it's not much:

Evidence that it was tyres, and not an engine failure that was responsible for the damage to the wing structure and subsequent fire is contained in the photographs taken as F-BTSC departed on its final flight.

The fire and breach in the wing structure are clearly shown as being in front of the engine, in a catastrophic engine failiure debris is thrown out explosively, but generally it is in the plain of rotation of the failed part where the most damage is done. In the above photo there appears to be little/no damage where you would expect to see it from an engine failiure. The fact that all the damage is forward of the engine is very unusual if it turns out to be an uncontained engine failiure.

Also, because of the way Concorde's engines are joined together, and because of the way they are attatched to the underside of the wing (not on pylons) they are encased in titanium, so that, in theory at least an uncontained engine failiure would actually be contained within the engine structure. There is no reason to doubt this, as many people have pointed out, Concorde is over-engineered and generally any given part will be stronger than it need be to perform effectively.

As for the thrust reverser, as OPNguy pointed out it is a bolt-on accessory, its workings are totally separate from the rest of the engine. It isn't a translating thrust reverser that is now almost universal where the engine cowl slides back and blocker doors come down inside the engine, it is the classic thrust reverser, as found on other turbojets with camshell doors which close behind the engine exhaust to deflect the thrust forwards, similar to the type found on 737-200s etc.

It is hard to see how any failure of a thrust reverser of this type would cause what occured at Paris. I would think the engine failure was a secondary cause of the accident from ingestion of tyre debris, not the initial failiure. From the photo all the flames appear to be coming from the breach in the wing structure. It's quite feasible that the engine failiure was non-catastrophic and caused by the ingestion of debris.

This has been a terrible accident, and a terrible loss.
I hope the cause can be discovered before too long. JAMES

You make a good point re: the plane-of-rotation aspect, assuming they breached the engine case. If engine failure *was* the initiating event (we sure can't see the *inboard* side of that pod), I'd then be surprised that departing engine parts could strike the underside of the wing at something far less than a 90 degree angle and breach the structure.

For those unconvinced on the tire theory, consider that...

1/ Tire debris, and not engine debris (so far), has reportedly been found on the runway; and

2/ The photo doesn't show any intact main gear tires on that truck, and

3/ The plane-of-rotation associated with any disintegrating tires/wheel frangments would presumable mean a more direct (less glancing) impact on the underside of the wing, and

4/ The failure mode has been seen before in the 7/14/1979 incident at IAD; and

5/ The appearance of the fire on the bottom of the Concorde's wing is very similar to that of the NASA Convair 990 I mentioned/linked earlier.

In the above Convair accident, large wheel fragments reportedly hit the wing at nearly 200mph, puncturing it, and allowing the fire. I rather doubt the designers of the Convair 990 or Concorde wings designed them to withstand the impact of such a heavy mass at such high velocities.

Also, as an aside, isn't bizzare how the media has fixated on the gear not being retracted? After considering the following two links, why would anyone *want* to at an airport with minimal obstacle?

OPNLguy,
Thanks for those links. If you want to put a direct hotlink in future, it's easy! Just put square brackets at the beiginning and end of the url, < >. Ie to post a link to http://www.xyz.com do this
(http://www.xyz.com) - but using square not rounded brackets.

You're also correct about the port maingear, the tyres definately don't appear to be intact.

While I agree that the tire scenario is likely, I still don't see proof as it has been quoted in the photo.

The fire and breach in the wing structure are clearly shown as being in front of the engine...

It's impossible to see from where the fire is pouring out of that wing. I certainly can not see it coming out in front of engine anymore than beside, or slightly aft, of the engine. If you look at the left engine nacelle, you will see that its profile is silhouetted against the bright orange flame, which, to me, would indicate that the flame is somewhat behind the engine.

Please explain better what is meant by "plane of rotation". The plane of rotation of the wheels is 360 degrees. A tire that bursts can spin out debris in all 360 degrees perpendicular to its axis. That would mean that debris can strike at any point along the wheel's path's 360 degrees, from the wing at the tip to the ground below. How does this fit one theory vs the other?

If the cowling of the engines is titanium and are designed to contain a blade separation, and I'm not sure that it was designed for that, would this not also mean that the engines would offer the same protection from an outside source of projectiles? Keep in mind that the speed of the tire's rotation is considerably less than the speed of a compressor or fan blade rotation. So, if very fast piece of metal can't get out, why then would a piece of metal, travelling much slower, get in?

There is a precedent to back up the theory that tire fragments punctured the fuel tank - this happened with another concorde, although in that indicident the leaking fuel did not ignite. Don't have the details, but I'll look it up and post it.

The photo isn't the clearest, and I'll take your point that the fire appears to be coming from a point roughly level with the engine intake. I don't know how familiar you are with Concorde's engines, but the intakes are much longer than the engines, which are situated some way back inside. The forward fanblades are actually located over one third of the way along, with the rest of the engine further back still.

Plane of rotation is difficult to explain easily. Basically if a turbine is rotating, its plane of rotation is the flat area, perpendicular to the axis of rotation, level with the fan blades. Put another way, say you put a laser on a fan blade, pointing along it from centre to tip and rotated the blade one full rotation - the infinitely large circle the laser would draw, theoretically, would enclose the plane of rotation.

In this context if there was an uncontained turbine failure you would expect the damage inflicted on the surrounding structure to be level with the failed turbine's position, with little damage forward/aft of this ie damage would be within the plane of rotation. This is because of the incredible speed of rotation and the huge centripetal forces within an engine, so that in a failure the parts of the engine fly out along the plane of rotation and the relative forward/rearward effect of any other forces on their trajectory is negligible.

I have a chart of the damage cause by the uncontained engine failure on the United DC-10 at Sioux City, the spread of damage for/aft of the position of the failed fan blade is no more than 6 inches either way, but it spreads a long way out in the plane of rotation.

Also, if you look at the engine nacelles, they are intact (although it's mostly cut off in this version of the picture, I've seen the full version) and in the Sioux accident there was damage all the way around the engine, which had there been a catastrophic failure would have been visible too.

So, as a quick summary, the damage to the wing is, in my opinion too far forward to have been caused by an uncontained engine failure.

The wheels of course also have a plane of rotation, but their rotational speed is compared to an engine turbine, tiny, and the forces involved nowhere near as great as you would find in an engine. Also in a tyre failure the debris is very likely to go sideways, as well as backwards, and there will generally be a much larger spread of debris/damage.

The titanium case of the engine was designed to contain a catastrophic engine failure, otherwise due to the close proximity of the engine to the wing and the other engine; any serious failure would strongly risk damage to either/both of these structures as well. Yes, the case would offer the same protection from other projectiles. Maybe I didn't express myself clearly...But the I meant that I thought the debris from the tyres had caused the engine failure by being ingested into the front of the engine. Also, just because the debris caused the engine to fail, it does not automatically mean the failure was catastrophic.

As a quick summary of what I think occurred, based on current evidence;
(1) Tyre blow-out
(2) Flying debris punctures wing underside and fuel tank, subsequent fire erupts
(3) Flying debris enters engines 1 and 2, causing (non-catastrophic) failure. Rubber passing through engine 1 would also explain why it failed twice before finally totally failing. Rubber passing through would cause much less damage than a piece of metal which may well stop it straight away
(4) Out of control, fuel-fed fire finally disables vital systems leading to loss of control

I hope I explained myself to your satisfaction, if not get back to me, and I'll do my best to clarify. I know I'm no expert, but I hope my theory is based on good information. Feel free to shoot big holes in it, I can take it!

After having looked at the above picture, I must agree that the tires could have disabled the engines, but not vice versa. The engines are quite further aback of the wheel boggies. If an engine threw a blade, the plane of rotation could not reach out to the tires. But if a tire blew, then its debris could be ingested into the engine and, I assume, disable it. The wing tank is vulnerable to both engine debris and tire debris. But by process of elimination, it was evidently tire debris that punctured it.

The only question that remains for me, is when did the Captain know he had an engine failure? By all witness accounts, it seems that the whole process started quite early in the take-off. It's hard to believe that the engine indicators only showed a problem after reaching V1. Prior to V1, the tower informed the captain that his plane was already a blow torch, meaning that the whole failure had already taken place. Why didn't he abort? It's almost as if the statistically impossible happened. Not one, but two engines failed, and they failed after V1 together. But according to the tower and other eyewitnesses, the problem occurred long before V1. So that leaves an unanswererd question. Sort of like the question asked of Reagan during the Iran-Contra hearings:
What did the captain know, and when did he know it?

Great use of the side-view photo, and I think it more clearly shows how readily main tire failure(s) could have initiated the whole accident sequence.

Looking at this side view, envision the main gears tires rotating, in this view, counter-clockwise. With Concorde tire fragments found on the runway and most airports very good about eliminating potential FOD hazards, it's quite likely they belonged to 4590. Assuming they did, and that one or more main tires tires came apart as the speed increased from brake release to their V1 and VR points, it's quite easy (i think) to envision the tire fragments rotating around (counter-clockwise, based on this view) and detaching due to basic centrigual forces. If a tornado or hurricane can drive a 2x4 through a tree, one can image the impact velocity of tire or wheel fragments (heavier mass) as they came off. How many lower wing skins are stressed for such an impact?

The previous head-on photo (with the flames) appears to show only one remaining tire on the outboard side of that truck, while the inboard side of the truck appears to show both tires gone. Assumng this to be the case, it could be argued that the underside of the wing could have received more damage from tire (or hot metal wheel) fragments, while the number 2 engine got enough ingested debris to cause internal damage/destuction.

Also looking back at this side-view photo, one could also say that any departing engine parts from a blown #2 engine could have also damaged the underside of the wing (and causing the fuel leak/fire). While that's certainly possible, it does not (IMHO) sufficiently explain the loss of the tires on that truck, since the gear is forward of where the engine's core is located. Engines can fail for other reasons of than tire or other FOD ingestion, but again, with tire fragments found on the runway, I think the trail starts there.

Sorry to be long, but one closing point/observation. Notice how the media has reported that the Captain "couldn't raise the landing gear" with the implication that this was all the result of the problems he was experiencing? If one goes back to that BBC story link I posted earlier re: the NTSB's comments and concerns from 20 years ago, you'll note that they recommended that the gear be kept *down* intentionally, rather than retract the gear and risk a tire blowing inside the gear well. Maybe, just maybe, the reports of "I can't raise the landing gear" were meant in the crew's context of "I can't raise the landing gear due to procedures and the risks noted by NTSB" versus assuming it was due to the mechanical inability to do so.

For a look at the failure mode(s) of a tire(s) blowing inside a gearwell, check out these links.

For whatever it's worth... Be interesting to know precisely where (i.e. how far from brake release at the end) it was...

PARIS (Reuters) - The flames spewing from the wing of an Air France Concorde minutes before it crashed last Tuesday were probably due to a massive fuel leak rather than a problem with one or more of the engines, investigators said Sunday.

The French Accident Investigation Bureau (BEA) said part of the debris from the plane found on the runway of Roissy-Charles de Gaulle airport, where it took off, appeared to come from a fuel tank.